Parabolic trough

Parabolic trough at Harper Lake in California

Parabolic trough

Quadric Parabolic Cylinder

Inside an enclosed CSP Trough

US Patent 1240890

Andasol Solar Power Station 2

Parabolic trough technology is a type of solar thermal energy collection system that uses parabolic mirrors to concentrate sunlight onto a receiver or absorber tube positioned at the focal point of the parabola. This technology is primarily used in solar power plants for electricity generation, as well as in some industrial processes that require heat. The concentrated sunlight heats a fluid flowing through the tube, which then is used to produce steam. The steam can drive a turbine connected to an electric generator for electricity production, or it can be used directly in thermal applications.

Design and Operation

A parabolic trough consists of a linear parabolic reflector that focuses the sun's rays onto a receiver tube located along the reflector's focal line. The reflector is typically made from polished metal or coated glass mirrors. The receiver tube, often called an absorber, is usually made of metal with a high thermal conductivity and is coated with a material that has high absorbance and low emittance to efficiently absorb solar radiation while minimizing heat loss.

The absorber tube is enclosed in an evacuated or argon-filled glass envelope to further reduce heat loss. The heat transfer fluid (HTF) flowing inside the absorber tube absorbs the concentrated solar energy, increasing in temperature to 400°C (752°F) or higher. Common HTFs include synthetic oil, molten salt, and water/steam. The heated fluid is then pumped through a series of heat exchangers to generate steam for electricity production or to supply heat for industrial processes.

Applications

Parabolic trough systems are versatile and can be used in various applications, including:

• Electricity generation: The primary application of parabolic trough technology is in solar thermal power plants, where it is used to produce steam for driving turbines and generators.
• Desalination: The heat generated by parabolic troughs can be used in desalination plants to produce fresh water from seawater.
• Industrial process heat: Industries that require high temperatures for processes, such as cement and chemical manufacturing, can utilize the heat from parabolic trough systems.

Advantages and Challenges

Parabolic trough technology offers several advantages, including:

• High efficiency: Parabolic troughs can achieve higher temperatures and efficiencies compared to other solar thermal technologies.
• Scalability: The technology can be scaled up or down to meet specific energy demands, making it suitable for both small and large-scale applications.
• Storage capability: The heat generated can be stored in thermal storage systems, allowing for electricity generation even when the sun is not shining.

However, there are also challenges:

• High initial costs: The upfront cost of parabolic trough systems can be high, although costs have been decreasing.
• Water usage: Cooling the system typically requires significant amounts of water, which can be a limitation in arid regions.
• Land use: Large-scale solar thermal plants require substantial land areas, which can impact land use and biodiversity.

Future Developments

Research and development in parabolic trough technology focus on increasing efficiency, reducing costs, and minimizing environmental impacts. Innovations include advanced materials for mirrors and absorbers, improved heat transfer fluids, and integration with other renewable technologies.